Method of dyeing an acrylonitrile copolymer with acid dyes and thiourea



Patented May 5, 1953 METHOD OF DYEING AN ACRYLONITRILE COPOLYMER WITH ACID DYES AND THIO- UREA George E. Ham, Dayton, Ohio, assignor, by mesne assignments, to The Chemstrand Corporation, a corporation of Delaware No Drawing. Application February 27, 1950,

'- Serial No. 146,633

This invention relates to a method of dyeing copolymers which are usually non-dyeable. More specifically the invention relates to a procedure for dyeing acrylonitrile polymers which ordinarily are not'dye-receptive. Polymers of acrylonitrile, such as polyacrylonitrile and copolymers of 75 or more percent of acrylonitrile and up to 25 percent of other monomers copolymerizable therewith, such as vinyl acetate, methyl methacrylate and methacrylonitrile, are well known to be excellent fiber-forming materials. However, due to poor dye receptivity, these known copolymers are of limited utility and of little value in the preparation of general purpcse fibers. In copending application No. 106,490, filed July 23, 1949, by George E. Ham and in application Serial No. 123,093, filed October 22, 1949, by George E. Ham, there are described and claimed non-dyeable acrylonitrile polymers which are capable of chemical reaction with a wide variety of reagents, including trimethylamine and ammonia, whereby the polymers are rendered capable of accepting dyes. This chemical reaction converts the copolymers containing a-chlorocarboxylate radicals into copolymers containing amino or quaternary ammonium salt groups which are believed to be responsible for improved dye receptivity.

The above described dye-receptive copolymers and the methods of preparing them are subject to inherent limitations due to the instability of the spinning solutions. In copending application Serial No. 146,632, filed February 27, 1950, by George E. Ham, there are described and claimed alternative methods of treating copoly mers of acrylonitrile and the polymerizable monomers containing. a-chlorocarboxylate radicals involving the treatment therewith with thiourea.

The primary purpose of the present invention is to provide a new procedure for preparing dyed fibers from acrylonitrile copolymers. A further purpose of the invention is to provide a means of eliminating the gelation frequently encountered with copolymers of acrylonitrile and unsaturated esters of a-halocarboxylic acids.

Suitable copolymers for the practice of this invention are copolymers of '75 to 98 percent of acrylonitrile and from two to 25 percent of an ester having the structural formula:

wherein X is a halogematom of the group con- 8 Claims. (Cl. 8--55) sisting of chlorine and bromine, R is a radical of the group consisting of hydrogen and alkyl having up to four carbon atoms, m and n are each whole numbers from zero to one, inclusive, and n is not greater than 112. Useful compounds for the practice of this invention include allyl chloroaoetate, vinyl chloroacetate, and methallyl chloroacetate. Although the copolymers of to 98 percent of acrylcnitrile and from two to 25 percent of the comonomers may be utilized in the practice of this invention, a preferred group of the copolymers are those of to percent acrylonitrile and from five to 20 percent of the said comonomer. The copolymers of '75 to 80 percent acrylonitrile have unusually desirable dye receptivity, but often are found to have less than the optimum fiber forming properties. On the other hand copolymers of 95 to 98 percent acrylonitrile and from two to five percent of the comonomer have unusually good fiber forming properties, but often lack sufiicient dye receptivity for general purpose utility.

The reactive copolymers may, if desired, contain small proportions of other monomers copolymerized therewith, for example up to ten percent of styrene, methacrylonitrile, alkyl acry-- lates, alkyl methacrylates, vinylidene chloride, alkyl fumarates, alkyl maleates or other polymerizable monomer. In general the proportions of other monomers should not be large or either the dyeability or the optimum fiber propertiesmay be lost.

- In accordance with the practice of this invention'a separate after-treatment of the fibers may be avoided by incorporating the thiourea in the dye bath. By this procedure the chloroacetate substituent is apparently reacted with thiourea and then with the dye in situ, whereby the modification of the copolymers into a dye-receptive 11 T -0Hlo-o-cHiso-NH201- It is believed that anionic exchange then occurs between the ionic halogen and the dye anion.

Regardless of the mechanisminvolved effective economical dyeing is achieved. These salt groups appear to be capable of reacting with acid dyes, particularly the sulfonic acid derivatives, to form a chemically bonded dyestuff which is fast to laundering and dry cleaning.

The thioureav in the: dye bath may be present; in a wide range of concentrations. Where the fiber is prepared from a copolymer of a substantial proportion of the a-halocarboxylate mono mer, or where the dyein is. conducted at. elevated temperatures or prolonged periodsof time, traces of thiourea will have a pronounced effect. On the other hand where the fibers are prepared from copolymers of a minor proportion of the reactive halogen containing monomer it may be necessary to use large quantities of thiourea, even up to the maximum solubility of: thiourea in the dye bath. The higher concur-- trations are especially useful in dyeing opera-- tions involving low temperatures and short immersion periods. I

The acrylonitrile copolymers maybe prepared by any conventional polymerization procedure-, but the preferred practice utilizes suspension polymerization wherein the copolymer is prepared in' finely divided form for immediate use in the fiber fabrication operations. The preferred suspension polymerization may utilize batch procedures, wherein monomers are charged with an aqueous medium containing the necessary catalyst and dispersing agents. A more desirable method involves the semi-continuous procedure in which the polymerization reactor containing the aqueous medium is charged withthe desired monomers gradually throughout the course of the reaction. Entirely continuous methods involving the gradual addition ofmonomers and the continuous withdrawal or copoly mermay also be employed;

The polymerization is catalyzediby' means at any water soluble perox-y compound, for example the potassium, ammonium and other water soluble salts of peroxy acids, sodium peroxide, hydrogen peroxide, sodium perborate, thesodium salts of'other peroxyacids, and any other water soluble compound containing a peroxy group A wide variation in the quantity of" achieved by vigorous agitation, itis generally desirable to promote-the uniform distribution of" reagents by using inert wetting agents, or emulision stabilizers. Suitablereagents for this purpose are the water soluble salts of fatty acids; such as sodium oleate and potassium stearate, mixtures of water soluble fatty acid salts; such as common soaps prepared by the saponification of animal and vegetable oils, the aminosoaps,'

such as salts of, triethanolamine and dodecylmethylamine, salts; of rosin acids and mixtures thereof, the water soluble salts of half esters of sulfuric acid and long chain aliphaticalcohols; sulfonated hydrocarbons. such as alkylaryr sul' inmates, and any other of" the wide variety of. wetting agents; which are in general organic;

compounds containing both hydrophobic and hydrophilic radicals. The quantity of emulsifying agent will depend upon the particular agent selected, the ratio of monomer to be used, and the conditions of polymerization; In. general, however; from 0 .01 to one percent by weight of the monomers may be employed.

The preferred methods of operation are those which, produce. a copolymer of very uniform chemical. and physical properties. Other characteristics of the: copolymer are frequently of great importance, for example the particle size of the dispersion which is primarily concerned with the-ease of filtration, the water to monomer ratio which must necessarily be low for the most economical production, and the yield and conversion: of the monomers to copolymer.

The. emulsion polymerizations are preferably conducted in glass or glass-lined vessels which are provided with a means for agitating the contents. Generally; rotarystirring devices are the most effective meansrof insuring'the-intimate contact of the-reagents, but: other methods may' be successfully employed, for example, by rocking or tumbling the reactors. The: polymerizationequipment generally: used is conventional in the art and the adaptation of a particular type of apparatusto the reaction. contemplated is within the province of one skilled in the art..

The. optimum. methods. of? polymerization for preparing fiber-forming acrylonitrile polymersinvolve the use. of polymerization. regulators to prevent the formation. of polymer units: of err-- cessive' molecular weight. Suitable regulators- I 7 are; the; alkyl; and; aryli mercaptans, carbon: tetrachloride; chloroform, dithioglycid'ol and alcohols. The; regulators. may be used in amounts varying from: .00].- to. twov percent on the weight of, the

monomerto: be polymerizedi When thepolymerization iscompl'ete, tbsp-01y men is, separated from the. aqueous. medium by any or the conventionally used methods; If" the dispersionv is very" stable. it. may be necessary" tobreak the; emulsion, for; example byadding; acids; bases, salts or'alcoholi. When the. optimum: procedures: above.- described' are used-,. the. polymer may be separated, from the aqueous. phase by: filtration. The resulting polymer in eithercase' may require washing operations to. remove-traces I of soluble; catalyst or' dispersing: agent.

' copolymers of acrylonitrile. used in: the practice: of. thisv invention, should: beof? uniform.

chemical. and physical properties and ofi relatively high molecular. weight. Molecular weightsas-low 55,. as: 1050.00; may; be; used. but. preferredi practiceinvolved the; use: of copolymers: with molecular weights between. 25,0 0Di and: 150,000..

The copolymers; of: acrylonitrile; and. the thiourea reactive comonomers are spun into fibers:-

conuentional procedures, The polymers. are dissolved, insuitable solvents; for: example. N;N-

dimethylformamide, N ,N-dimethylacetamide and:

1 I,N-dimethylmethoxyacetamide; and the; sold- 1310118 extruded. througha suitable die, or aspizrneret containingv av plurality; of: apertures into a. medium which. removes. the solvent 2 and. percipiitates the; polymer: in a. continuous form. The

spinning: medium may: be. a liquid medium, for

example: glycerine, water, or aqueous solutions of salts, acidsorbases; oraqueous mixtures' of desirable; physical properties than is prepared by precipitation into water alone. The fiber may also be extruded into air or other s us med um by conventional dry spinning methods.

Further details of the practice of this invention are set forth with respect to the following specific examples.

Example 1 A copolymer of 91 percent acrylonitrile and nine percent of allyl chloroacetate was dissolved in N,N-dimethylaoetamide and extruded through a spinneret having 30 apertures, each .0035 inch in diameter, into a mixture of two parts of Water and one part of N,1 T-dimethylacetamide at 40 C. The fiber so prepared was stretched 3.3 times in an atmosphere of steam at 130 C. The fiber was then dyed for thirty minutes at 100 C. in a bath consisting of 60 mls. of water, 1.3 mls. of two percent Wool Fast Scarlet (C. I. 252), 5.9 mls. of three percent sulfuric acid, and 0.1 gram of thiourea. Complete dye bath exhaustion was obtained and the fiber Was dyed a deep scarlet. The tensile strength and thermal resistance of the yarn were not affected by the procedure. A sample of the same fiber treated in a similar dye bath without the use of thiourea did not absorb an appreciable amount of the dye. A skein dyed as above with 40% of the fiber weight as thiourea gave dye bath exhaustion in minutes.

Example 2 The procedure of the preceding example was duplicated using Alizarin Light Blue 4G1. and Wool Fast Yellow, except that 0.2 gram of thiourea were used in the dye bath. Deep shades of colored fibers were thereby prepared.

Example 3 The procedure of Example 1 was repeated except that a copolymer of 94.7 percent of acrylonitrile and 5.3 percent of vinyl chloroacetate was used. A one hour dye treatment at 100 C. with a thiourea concentration equivalent to 20% f the fiber weight exhausted the dye bath.

Example 4 A copolymer of 95.8% acrylonitrile-4.2% allyl chloroacetate was spun from a 20% solution in dimethylacetamide into a mixture of 67% dimethylacetamide-33% water at 40 C. and stretched in steam at 30 p. s. i. 200%. The fibers were dyed as in Example 1 with Wool Fast Scarlet to which an amount of thiourea equal to the fiber Weight was added. The dye bath was exhausted within ten minutes and a bright scarlet fiber was produced.

I claim:

1. A method of dyeing a fiber of a copolymer of '75 to 98 percent by weight of acrylonitrile and from two to 25 percent of a compound having the formula:

wherein X is an atom of the group consisting of chlorine and bromine, is a radical of the group consisting of hydrogen and alkyl radicals having up to four carbon atoms, m and n are small whole numbers from zero to one, inclusive, and n is not greater than m, which comprises treating the fiber with an aqueous bath of an acid dye containing thiourea.

2. A method of dyeing a fiber of a copolymer of to 98 percent by weight of acrylonitrile and two to 25 percent of allyl chloroacetate, which comprises treating the fiber in an aqueous dye bath of acid dye in the presence of thiourea.

3. A method of dyeing a fiber of a copolymer of 75 to 98 percent by weight of acrylonitrile and two to 25 percent of vinyl chloroacetate, which comprises treating the fiber in an aqueous dye bath of acid dye in the presence of thiourea.

4. A method of dyeing a fiber or a copolymer of 75 to 98 percent by weight of acrylonitrile and two to 25 percent of methallyl chloroacetate, which comprises treating the fiber in an aqueous dye bath of acid dye in the presence of thiourea.

5. A method of preparing a dyed fiber, which comprises treating in an aqueous dye bath of acid dye a fiber of a copolymer of to percent by weight of acrylonitrile and from five to 20 percent of a compound having the formula:

wherein X is an atonrof the group consisting of chlorine and bromine, R is a radical of the group consisting of hydrogen and alkyl radicals having up to four carbon atoms, m and n are small whole numbers from zero to one, inclusive, and n is not greater than m, said dye bath containing thiourea.

6. A method of preparing a dyed fiber, which comprises treating in an aqueous dye bath a fiber of a copolymer of 80 to 95 percent by weight of acrylonitrile and from five to 20 percent of allyl chloroacetate, said dye bath containing an acid dyestufi and thiourea.

7. A method of preparing a dyed fiber, which comprises treating in an aqueous dye bath a fiber of a copolymer of 80 to 95 percent by weight of acrylonitrile and from five to 20 percent of vinyl chloroacetate, said dye bath containing an acid dyestufi and thiourea.

8. A method of preparing a dyed fiber, whic comprises treating in an aqueous dye bath a fiber of a copolymer of 80 to 95 percent by weight of acrylonitrile and from five to 20 percent of methallyl chloroacetate, said dye bath containing an acid dyestuff and thiourea.

GEORGE E. HAM.

References Cited in the file of this patent UNITED STATES PATENTS Number 

1. A METHOD OF DYEING A FIBER OF A COPOLYMER OF 75 TO 98 PERCENT BY WEIGHT OF ACRYLONITRILE AND FROM TWO TO 25 PERCENT OF A COMPOUND HAVIN THE FORMULA: 